1. Field of the Invention
The invention relates to a method for reducing the stress on a titanium nitride layer, and more particular to a method for reducing stress on a titanium nitride layer deposited by collimator sputtering, and improving a peeling problem in the subsequent processing.
2. Description of the Related Art
In the semiconductor fabricating process, the sputtering technique is very important for the formation of a variety of metal layers, especially an aluminum alloy or a barrier layer. However, the disadvantage of the conventional sputtering method is that the step coverage of a film deposited by sputtering is poor. As the integration of semiconductor devices grows higher and higher, this problem becomes more serious. Thus, another method of sputtering, that is, a collimator sputtering technique, is proposed. The collimator sputtering provides a good step coverage on the bottom of a trench structure for depositing a film. To apply collimator sputtering technique in metal layer deposition, the geometry design can reach to 0.35 .mu.m to 0.25 .mu.m. However, compared to the conventional sputtering method, the stress on titanium nitride formed by collimator sputtering is much larger.
Referring to FIG. 1, a cross-sectional view of a convention method for depositing a titanium nitride by the collimator sputtering technique is illustrated. A collimator 12 is positioned between a metal target 10 and a substrate 11. The substrate 11 comprises a trench structure 14, and a titanium nitride layer 16 is formed by aligning the collimator 12 with the trench 14. The profile of the collimator 12 has a cellular structure and is composed by several hexagonal tubes. The path angle of the atom beam sputtered from the metal target has to be small enough to pass through the collimator 12 and to reach the surface of the substrate 11. Therefore, using the collimator 12 can filter out the large angle sputtered deposition. Obviously, the deposited titanium nitride layer 16 deposited on the bottom of the trench 14 has a better step coverage than by using a conventional sputtering method.
However, the metal layer, for example, a titanium layer, formed by the collimator sputtering technique has a preferred orientation, such as &lt;100&gt;-orientation of lattice arrangement no matter by it is a barrier layer or an adhesion layer. Thus, the titanium nitride layer lattice has an identical arrangement orientation, and therefore, a larger stress. For example, the stress on a titanium nitride layer with a thickness of about 600 .ANG. is about -1.64E10Nt/m.sup.2, while the stress on a titanium nitride layer with a thickness is about 800 .ANG. is about -1.25E10Nt/m.sup.2.